0:19Skip to 0 minutes and 19 secondsIn the mid '70s, scientists alerted policymakers and the world in general of the potential harmful effects of the CFCs, Chlorofluorocarbons, in the depletion of ozone. Ozone is extremely important because it protects the earth from harmful UV radiation. So depletion of ozone, especially experienced over Antarctica, but in general experienced globally, could be potentially really harmful. Because you would increase the amount of irradiation reaching the surface of the earth and consequently skin cancer, cataracts, or affect vegetation in a negative way. And because of the concern that was raised by these so-called ozone holes, policy makers got together in 1987 and ratified what's known as the Montreal Protocol in order to stop the emissions of these CFCs.

1:18Skip to 1 minute and 18 secondsAnd it was actually images like this one that were incredibly instrumental in convincing the public opinion, but also the policymakers, on the importance of the seriousness of the ozone problem. And it was also a visual impact. You see this big hole right over Antarctica. And because of that there was an immediate reaction. And at the time, to sign this protocol was very quick. And not only that, but it was ratified almost immediately by all countries. And now the effect of this treaty can be actually observed in a recovery of the ozone to levels prior to the depletion of the '70s and '80s.

2:06Skip to 2 minutes and 6 secondsAnd you can see here for example in this panel, like progressively, this is actually a product based on model reanalysis. So accumulation of data from satellite and the model background to produce this reanalysis of the ozone hole. And you see from 2006 to 2010 a recovery of the ozone and a diminishing of the holes on whole. This is a great example of how satellite data could inform decisions, important policy decisions, that were actually crucial to really avert a major environmental disaster.

In this video, Dr Angela Benedetti highlights the importance of past and current stratospheric ozone observations, and explores the key role that Earth observation played in delivering the Montreal Protocol and in monitoring its effectiveness.

Stratospheric ozone acts like a protective blanket located high in the atmosphere, shielding life on Earth from harmful ultraviolet (UV) radiation coming from the Sun. In the 1980’s scientists observed that this important layer was slowly depleting due to the excessive use of long-lived manmade chemicals called chlorofluorocarbons (CFCs). As the released CFCs circulated into the stratosphere, a process that can take a few years to occur, they broke down and produced highly reactive chlorine atoms. Each chlorine atom can break apart more than 100,000 ozone molecules, so the stratospheric ozone layer was rapidly being destroyed, along with its ability to block out UV rays.

Earth observation data played a pivotal role in the events leading up to the signing of the Montreal Protocol in 1987, helping to ban the production and use of CFCs and forcing their replacement with other chemicals. Observations from satellite instruments provided powerful and compelling information that confirmed initial observations of ozone depletion made by balloons, and then alerted scientists, and later the public, that this process was occurring above huge areas over Antarctica. The issue was soon recognised worldwide as an extremely serious environmental threat. Since the ratification of the treaty, satellites continue to provide key observations of the state of the ozone hole, allowing us to monitor its recovery.

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Dr Angela Benedetti

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